I have trouble falling asleep also. I have a horrible summer sleeping schedule of 5AM to 1PM. I only FORCE myself to fall asleep at 5AM because the sun starts to come up, and once the sun is up, it's nearly impossible for me to fall asleep. Even so, I can't fall asleep at a normal hour.
I even tried joining a gym and going 3 days in a row, but I still didn't get that "exhausted" feeling you're supposed to get. *sigh* You're not alone OP!